Electrostatic discharge (ESD) protection in the electronic and integrated circuit arts is a technology that attempts to address, among other things, the small sparks and flashes of static electricity that are sometimes encountered by people in dry climates or in drier months of the year, as when walking across a carpet or taking off a garment. These sparks can represent thousands of volts of static electricity that generally involve such low amounts of electrical current that they pose no risk or harm to people, but do call for well-considered protective measures to avoid damage to the microscopically small circuitry elements of today's integrated circuits and electronic devices.
Automotive and other vehicular applications of integrated circuit electronics also need to be resistant to ESD, and ESD without limitation includes herein various kinds of transient noise and electrical discharges regardless of origin. Moreover, industrial environments in which such integrated circuits and system products are made and used can also cause ESD conditions that can cause expensive failures in manufacture and problems in industrial use. In extreme cases the availability of supply, cost of manufacture, and ultimate price of particular integrated circuits and system products could be affected.
ESD events are stealthy and largely unpredictable in their particular circumstances when they happen in the field to a device in use, and their damage would be expensive to fix and prevent at that point even if an exact destroyed or damaged spot in the IC could be found. Furthermore, subtle undesirable interaction effects in circuitry can be caused by ESD, and thus no actual microscopic physical destruction due to ESD may exist. Accordingly, introducing ESD protection measures beforehand is vital to prevent not only ESD damage but also prevent any undesirable operational effects that interfere with the way the circuits are intended to work. However, the wide variety and complexity of integrated circuits and system products also increases the variety of ways that an integrated circuit might fail operationally when subjected to even a specifically-controlled ESD event and even when some basic ESD protection to prevent physical destruction of the chip is present near the pins of the chip.
With the increasingly pervasive presence and significance of personal computers and mobile consumer electronic devices in industrial and personal consumer use, for instance, the importance of recognizing electrostatic discharge conditions and protecting integrated circuits from their effects has never been greater.
Challenges in the ESD protection art continue to present themselves not only as the integrated circuit structures become increasingly complex and sophisticated and microscopically ever smaller, but also as the operations demanded of integrated circuits call for very high rates of speed of digital logic operations and/or executing instructions and data processing with which ESD can interfere. These smaller structures and higher rates of instruction and data processing are supported by fast actuating circuits called clock circuits. To generate the very high clock frequencies that support high-performance electronic devices on the order of hundreds of megahertz or above one gigahertz (billion cycles per second), high frequency clock oscillator circuitry and clock-multiplying phase lock loop (PLL) circuitry are used.
Significant technological departures are needed to solve categories of ESD problems, especially problems associated with the main support and warning circuits, as more specifically described hereinbelow.